Three years after the Sri Lankan government brutally quashed its long-running Tamil separatist insurgency, Sri Lankans visiting India's southern state of Tamil Nadu are suffering a delayed backlash.

On Monday, 184 Christian pilgrims from Sri Lanka visiting Tamil Nadu were forced to take refuge from protesters in a church.

They cut their visit short and turned back - and were pelted with stones on the way to the airport a day later.

Colombo has asked its citizens not to visit Tamil Nadu until further notice.

"In our 15 years of experience of pilgrimage... it's the first time that we have faced problems. We were unaware of the hostility towards Sinhalese here," Selin, a 55-year-old pilgrim, told an Indian newspaper.

The plight of Sri Lankan Tamils in Sinhalese-dominated Sri Lanka remains an emotive and political issue in Tamil Nadu, home to 60 million Tamils.

Regional parties AIADMK and DMK, a member of the ruling federal coalition, often push the federal government to take a tough line with the Sri Lankan government, like investigating human rights violations against the Tamil minority.

Sri Lankan President Mahinda Rajapaksa is credited with ending the 25-year civil war against the Tamil Tiger rebels in May 2009. In fact, Colombo managed to quell the insurgency, thanks to solid intelligence and diplomatic support from India, which helped choke off the supply routes to the Jaffna Peninsula.

But the Sri Lankan President faces international criticism, including from India, for his handling of the aftermath of the war and for delays in investigating alleged human rights violations during and after the war.

Over the weekend, Tamil Nadu Chief Minister J. Jayalalithaa, who has been trying to outdo her rivals in scoring political points over the Sri Lankan Tamil issue, sent back two Sri Lankan football teams and suspended an official for allowing one of the teams to have a friendly match with an Indian team.

"It is a manifestation of a slide back in the relationship between India and Sri Lanka," said Professor S. D. Muni, a foreign policy expert and senior visiting scholar at the Institute for Defence Studies and Analyses in Delhi.

India is pushing Sri Lanka to give more local power to Tamil-dominated provinces, which has not gone down well in Colombo.

India also voted for a United Nations Human Rights Council resolution in March asking Sri Lanka to "credibly investigate" allegations of violations in the war against the Tamil Tigers.

It has not helped that New Delhi is worried about growing Chinese investments and influence in Sri Lanka.

Chinese Defence Minister Liang Guanglie arrived in India for a visit this week, following a five-day visit to Sri Lanka where he was compelled to explain that Beijing's stepped-up engagement in South Asia was not aimed at a "third party", namely India.

During the visit, General Liang announced new aid to build and modernise Sri Lankan military training.

At the same time, Sri Lankans training with India's military are having a hard time. Jayalalithaa has written to ask Prime Minister Manmohan Singh to send back two Sri Lankan defence personnel training in military facilities in her state, saying it showed "scant regard for the views of the government and the people".

Last month, nine Sri Lankan air force personnel receiving training in Chennai, the capital of Tamil Nadu, were shifted to Bangalore, which is in the neighbouring state of Karnataka, following protests.

India's Ministry of External Affairs assured Colombo that it would take measures to protect Sri Lankans in India.

But the rhetoric and protests in Tamil Nadu are building up at a time when Rajapaksa is getting ready to visit India to lay the foundation stone of the Centre for Buddhist studies in Madhya Pradesh state on September 21, at the invitation of Bharatiya Janata Party leader Sushma Swaraj.

Sri Lankan Economic Development Minister Basil Rajapaksa, the President's brother, is also expected in India soon for talks.

"Whatever the differences and opposition that exists regarding the Sri Lankan government's approach to the Tamil question in Sri Lanka, nothing should be done to disturb people-to-people relations," the Communist Party of India (Marxist), an opposition party at the federal level, said in a statement on Tuesday.